Estrous Cyclicity of Uterine Glucose Oxidation and Glycogen Synthesis in the Hamster1

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Abstract
Changes in glucose oxidative capacity, incorporation of glucose into glycogen and glycogen content were measured in uterine segments removed at 12 h intervals from normally cycling hamsters. Glycogen content was highest at proestrus (day 4), about 12 h after peak levels of glucose incorporation into glycogen on day 3. The production of 14CO2 from labeled glucose was highest on days 2 and 3 of the cycle. Observed increases in these measures of carbohydrate metabolism correlate with increasing estradiol (E2) and decreasing progesterone (P) secretions known to occur at the time of the luteal-follicular shift (days 2-3). At estrus (day 1), uterine carbohydrate metabolism is minimal compared with days 2 and 3. In ovariectomized hamsters, E2 treatment elevates both uterine 14CO2 production from glucose and glucose incorporation into glycogen for several hours. These effects are depressed by short intervals of P treatment and cannot be restored by additional exposure to E2. E2 apparently is unable to sustain certain target tissue responses in the presence of P. Similar inhibition and refractoriness caused by P could play an important role in mediating the estrous cyclicity of uterine carbohydrate metabolism.